Assets/$$anonymous$$uel/RussianAirbaseV2/TerrainSize.cs(12,17): error CS1061: Type UnityEngine.GameObject' does not contain a definition for terrainData' and no extension method terrainData' of type UnityEngine.GameObject' could be found. Are you missing an assembly reference?

So it turns out that if you set the terrain size in the terrain datas object initialization, and then set the height data later, the size gets overwritten. So it is important to set the terrain size after the height data has been set.

Via script i don't think it is possible, but you can click on "terrain" on the top left screen, click on "set resolution...", then you can edit the width, length, and height of a terrain. But via script, i have no idea. Ands since when you make a nice terrain and change the resolution, it goes flat and you must remake the map... So editing the size inside of the game qith a script seems improbable.